Sianturi, R., J. E. Sitohang, and R. Hartati. “Enhancing Speaking Motivation Through Duolingo and NLP Presupposition: "There Is No Failure, Only Feedback"”. DEIKTIS: Jurnal Pendidikan, Bahasa Dan Sastra, Vol. 5, no. 3, July 2025, pp. 1802-10, https://www.dmi-journals.org/deiktis/article/view/1856.